Process for treating material containing copper and tin



Patented Mar. 28, 1939 UNITED STATES PROCESS FOR TREATING CON- TAINING COPPER AND TIN Max F. W. Heberlein, Rahway, N. J., assignor to The American Metal Company, Limited, New York, N. Y., a corporation of New York Application February 10, 1938, Serial No. 189,171

3 Claims.

v This in an invention for the treatment of materials containing copper and tin and other metal or metals and more particularly for the recovery of copper, tin and other constituents from such material.

The invention has further reference to a novel method involving roasting of material containing copper and tin with a chlorine-containing agent under controlled conditions to convert the copper into a form so that it may be readily removed from the tin. Various other objects, advantages and features of the invention will become apparent from the following detailed description.

, ence is had to the following description and to the drawing accompanying it, which consists of a diagrammatic representation or fiow sheet of the manner in which I now prefer to practice the invention.

In the operation (both in the United States and abroad) of mixed-metals plants, which are forced to treat raw materials containing copper and tin besides other metals, an undesirable by-product is usually obtained, which is generally known as white matte". The recovery of themetal values contained in this by-product has always been very costly. The treatment of this white matte and similar material presents a considerable difliculty on account of the chemical and metallurgical properties of its constituents. The peculiarity of the material is that it contains many of the commonly encountered metals which sometimes occur as intermetallic compounds such as combinations of tin with copper, or antimony, or arsenic, or nickel, or iron and copper with antimony or sulphur and iron with antimony or arsenic or sulphur and others. These compounds appear to be held together either by metallic lead or a lead-tin alloy which acts as a binder. In attempting to recover the metal values from this complex material, plain oxidizing roasts with various modifications, followed by an acid leach, were tried; also a sulphating roast was tried, but the results were not satisfactory.

I have found in accordance with my invention that the grinding and roasting of such material containing copper and tin with a chloridizing agent, under controlled conditions, including a temperature of about 800-900 F., results in converting the copper into a form so that it is soluble in dilute sulphuric acid and may be removed by leaching therewith and filtration. In order to make this conversion, it has been found that the addition of salt (NaCl) greatly aids in bringing about the desired chemical results. It has been found that about 15% by weight of salt added to and mixed with the finely ground material before roasting has given excellent results. The proportion of salt may of coursebe changed for different materials.

The material containing copper and tin may be white matte referred to above or other copperand tin-bearing materials such as for example lead-copper matte and. copper-tin ore concentrates. f

Although not restricted thereto, my invention has been successfully applied to materials analyzing as follows:

. Per cent Copperz--. 10 to 50 Tin 20 to Lead 5 to 20 Arsenic 1 to 10 Antimony 1 to 5 Nickel i to 5 Iron A. to 2 Sulphur /g to 5 In accordance with my invention and in order to accomplish satisfactory calcination, the white matte or other like material is broken down to a particle size of approximately 4 inch. The crushed material is then ground in wet or dry condition. If ground dry the mill-feed is sprayed with water to prevent dusting. There is added to the mill-feed salt (NaCl) in the proportion of about 15% of the weight of the crushed mate,- rial. In the rod mill the material is crushed to about a 50 mesh particle size. Occasionally such a complete grind is difficult or impossible to accomplish. This is apt to be so when the ductile or semi-ductile materials flatten in the mill instead of being broken up. If such material is encountered it is sieved out and returned to the refinery. The discharge of the mill is sprayed with water to minimize dusting.

The finely ground material is then charged, for example, to the top hearth of a roasting furnace of the Wedge multiple hearth type although other roasters, including hand masters, may be used. Oil burners on the middle hearths of the Wedge type, are used to control the furnace temperature in a manner such that a minimum temperature of about 800 F. is maintained on these hearths The temperature should preferably not rise much above 900 F. An oxidizing atmosphere is maintained above the material being subjected to the temperature of 800-900 F. The top hearth is heated by radiation from the hearths below, and serves as a spreader and drier for the material The material is passed through at a rate so that substantially all of it a is subjected to a temperature of the order menwill easily be ground fine;

tioned.

After the calcines have been taken from the roaster they may be subjected to a regrinding and second roasting usually without additional salt. If there are any unroasted interiors of the calcined granules which are not completely oxidized or if there are any metallics in the discharge from the roaster which remain unoxidized after the first roast then this regrinding and re-roasting makes the resultant product much more suitable for the leaching operation which follows. The regrinding will break open calcined granules and expose the unroasted interiors and the metallics which have become partly oxidized and brittle Furthermore if there are any silicates present it ,is desirable to break them down by a second roast which apparently causes a reaction between the copper silicate. and sodium oxide, NazO, which has been formed during the first roast. Any copper silicates which have been formed during the first roast are obviously decomposed during the second roast, probably due to some chemical reaction between the copper silicate and NaO, which had been formed during the first roast. Most likely the following reactions occur at elevated temperatures during the second roast:

It was also observed that any CuzClz, which had been formed during the first roast, is oxidized to an acid soluble form; probably CllClz and CuO, during the second roast.

The calcines discharged from the roaster after one or two roastings are transported to the leaching plant. Prior to leaching they are pulverized to insure a maximum leaching efiiciency. Leach ing is effected with dilute sulphuric acid and the leach-slurry goes to a filter press where the filtrate passes to the cementation tanks and is treated with scrap iron to remove copper or the copper is electrolytically removed. The filter cake from the press is smelted to recover the values therein. During the pressing .process the filter cake is washed and the first wash water is returned to dilute the. sulphuric acid used for leaching the following batch of ground calcines. Subsequent wash waters are discarded.

The following example is an embodiment of the preferred manner of carrying out my invention. It is to be understood that the example is illustrative and that the invention is not to be considered as limited thereby except as indicated in the appended claims.

150 lbs. of high copper white matte were crushed to a particle size of approximately A, inch. The material analyzed:

Per cent Copper 35.5 Tin 30.75 Lead 11.8 Nickel 0.45 Arsenic 3.7 Antimony 1.6

non small amount-not determined.

charged to the roasting furnace.

The crushed material was then charged to a rod mill. There was added to the mill-feed approximately 22% lbs. of salt (NaCl) for the 150 lbs. of crushed white matte. The crushed matte and salt were intimately mixed. The mixture was The charge was roasted at 800-900 F. for a period of 4 hours and during this time the charge was rabbled. The roasted calcines weighed approximately 197 lbs. and analyzed:

' Per cent Copper 25.3 Tin 23.9 Lead 8.1 Nickel 0.34 Arsenic 2.9 Antimony 1.3

Iron, small amountnot determined.

The calcines were then pulverized. No second roasting was necessary. The pulverized calcines were then leached with about 127 gallons .of hot dilute sulphuric acid of about 10% strength in a lead-lined wooden tank. From the leaching tank the leached pulp or slurry was pumped to a filter press. It was there filtered and washed under pressure. The leached residue Weighed 100 lbs. and analyzed:

1 Per cent Copper 1.05 Tin' 45.8 Lead 12.9 Nickel 0.30 Arsenic -1 1.2 Antimony 2.0

Iron, small amount-not determined.

.cove'r tin and other values therefrom.

It is believed that the action of tin and copper under the conditions of my process may be explained as follows:

'I in, which is present in the white matte as an believed to react with the sodium of the salt (NaCl) and consequently does not form a volatile tin chloride. The liberated chlorine is therefore allowed to react with other metals such as copper and lead. Because of the strongly oxidizing conditions in the furnace and the presence of other metalloids such as arsenides and antiinonides which have a higher chemical affinity for sodium or sodium oxide than tin, the stannates formed will decompose to form anhydrous stannic acid (SnOz). None of the intermediate tin-bearing compounds in this series of reactions is volatile at the prevailing roasting temperatures which explains the complete tin recovery in the calcines. With progressive calcination the SnOz becomes increasingly acid insoluble.

Copper, upon liberation fro-Inthe stannides, arsenides, antimonides, etc. is oxidized to copper oxide CuO, which will combine with any acid radical if present, to form the corresponding copper salt. Any acid radicals present,which upon oxidation form acid soluble copper salts, will not interfere with the successful removal of copper.

The filter cake, which had a moisture con-.

formation of NaCuCla, which is slightly volatile at a low red-heat. n continued calcination this compound is probably converted into 0112C]:

and/or CuClz, CuO and NaaO.

In addition the action of lead, nickel, arsenic,

.iron, sulphur and antimony apparently is as follows:

Lead is partially converted into sodium-leadchloride, which may volatilize at temperatures which may occur during the process. A volatilization loss of about has been usually observed during the test-work. The final oxidation product of this constituent of the charge has been found to be lead oxide, PbO. Upon leaching, insoluble lead sulphate (PbSOl) is formed, which remains with the tinoxide (S1102) in the leach residue as filter cake. I

Nickel is probably oxidized to nickel oxide N10, which is soluble in sulphuric acid but if NiO crystallizes due to calcination it becomes acid insoluble. A partial crystallization of N10 apparently takes place during the roast. Upon leaching, varying amounts of N10 combine with the sulphuric acid to form soluble nickel sulfate.

- Whatever quantity of MD has been crystallized during the roast, will remainas acid insoluble NiO in the filter cake.

Arsenic is oxidized to the higher oxide and forms one or several of the various types of arsenates, which are not volatile at the prevailing roasting temperatures. The formation ofl arsenates is also the reason for the relatively high acid-solubility of the roasted arsenic,

. -Antimony is preferably oxidized to antimony oxide'SbzOr, which is the most stable antimony oxide in the "dark red temperature range, although other oxides, SbaOa or SbzOs may form under certain conditions. 4

The formation of the various oxides of antimony, depending on prevailing furnace conditions explains the veryuncertain elimination of antimony during roasting and leaching. The characteristic physical'properties of the various antimony oxides, which influence the elimination of this impurity are:

513204 is non-volatile and insoluble in dilute acids, I

Sbz03 is volatile and acid soluble,

SbzOs is non-volatile and acid soluble.

Iron is most likely oxidized to FezOa, which is acid insoluble and remains in the leach residue.

Sulphur is oxidized to either S0: or $03. In the latter case it forms sulphates with the, metal oxides. v

The treatment of other copper, tin-bearing materials such as lead-copper matte and coppertin ore concentrates, may be carried out in substantially the same manner, as mentioned above.

While the invention has been described with respect to a preferred example which gives satisfactory results, it will be understood by those skilledin the art after understanding the invention; that various changes and modifications may be made without departing from the spirit and scope of the invention and it is intended in the appended claims to cover all such changes and modifications.

What is claimed as new and desired to be secured by Letters Patent is:

1. A process of the kind described which comprises taking a material containing about 10 to 50% copper and about 20 to 60% tin including intermetallic compounds, mixing salt with the material and roasting the mixed material at a temperature of the order of 800 to 900-F. to convert copper and tin into oxides.

2. A process of the kind described which comprises taking a material containing about 10 to 50% copper and about 20 to 60% tin including intermetallic compounds, grinding said material into particles, mixing at least 15% of sodium chloride with the ground material and roasting the mixed material at a temperature of the order of 800 to 900 F. to convert copper and tin into oxides.

3. A step in the process of treating copper and tin containing material including an intermetallic compound which consists in heating to about 800 to 900 F. a mixture containing salt and said material containing about 15 to 50% copper and about 20 to 60% tin in finally ground F. W. HIEIBERLEIN. 

